1. Field of the Invention
The present invention relates to a particle monitor system and a substrate processing apparatus, and in particular to a particle monitor system that detects particles in a chamber or an exhaust pipe of a substrate processing apparatus.
2. Description of the Related Art
Substrate processing apparatuses are known that have a chamber in which a wafer as a substrate is housed, and an exhaust pipe through which particles and gas are exhausted out of the chamber. In this substrate processing apparatus, a wafer housed in the chamber is subjected to desired processing such as etching processing or CVD (chemical vapor deposition) processing, but while the processing is being repeated, particles resulting from reaction product or deposit are produced in the chamber. As the number of particles in the chamber increases, the number of particles that become attached to wafers increases, resulting in the yield of semiconductor devices manufactured from the wafers decreasing. It is thus necessary to detect particles in the chamber on a regular basis.
As a method of detecting particles in the chamber, there is known a method in which the number of particles flowing in the exhaust pipe is detected, and the number and sizes of particles in the chamber are estimated from the detection result. In this detection method, an ISPM (In Situ Particle Monitor) using scattered light is typically used. As the ISPM, there is known an ISPM that has a laser diode that irradiates a laser beam toward particles, and a CCD light-receiving element that receives scattered light produced at this time, so that the sizes and the like of particles are found based on the amount of the received scattered light (see, for example, Japanese Laid-Open Patent Publication (Kokai) No. H05-206235). In this ISPM, scattered light is produced in all directions from a particle, but because the CCD light-receiving element does not face the entire surface of the particle, the CCD light-receiving element can receive only a one-direction component of the scattered light produced in all directions from the particle.
On the other hand, in recent years, as semiconductor devices manufactured from wafers have become miniaturized, the width of trenches and the diameter of via holes formed on wafers have decreased to about several tens of nanometers. Moreover, an interlayer film of a semiconductor device has been required to be made thinner. For this reason, the size of particles that should be detected in a chamber of a substrate processing apparatus is now about several tens of nanometers.
However, because the conventional ISPMs using scattered light merely receive a one-direction component of scattered light produced in all directions from a particle as described above, it is impossible to detect the particle unless it is a very large particle that can produce a large amount of scattered light. For example, the lower limit size of a particle that can be detected is 200 nm. Namely, the conventional ISPMs using scattered light cannot detect fine particles which are several tens of nanometers in size.